A carrier sense multiple access (CSMA) technology is a channel sharing method applied to a wireless communications system. A communications device makes a channel access decision by sensing a channel for idle or busy. Determining, by the communications device, whether the channel is idle or busy is referred to as clear channel assessment (CCA). When a radio resource is idle, multiple nodes may contend for the idle radio resource. If a node learns, in a sensing manner, that the radio resource has been occupied, or after a node obtains a notification that the radio resource is to be occupied, the node does not occupy the radio resource.
With the development of technology, a multiple-input multiple-output (MIMO) technology finds wider applications. A node that supports the MIMO technology has a relatively strong anti-interference capability. If two neighboring nodes (for example, a node 1 and a node 2) that support the MIMO occupy a same radio resource, the node 1 may not cause interference to data transmission of the node 2. Likewise, the node 2 does not cause interference to data transmission of node 1 either. However, if the CCA in the prior art is applied, the node 2 may consider that a radio resource used by the node 1 has been occupied. In this case, the node 2 does not occupy the radio resource for data transmission. In this way, the relatively strong anti-interference capability of the MIMO technology cannot be effectively utilized as an advantage, and therefore a waste of the radio resource is caused.